From 08f6b8673adea23d2e96ca983f5d843c17b9a0e7 Mon Sep 17 00:00:00 2001
From: Peter Zhu <peter@peterzhu.ca>
Date: Mon, 5 Jan 2026 18:31:38 -0500
Subject: [PATCH] [ruby/mmtk] Set MMTK_DEBUG in C compiler for debug builds

https://github.com/ruby/mmtk/commit/12a3904b04
---
 gc/mmtk/extconf.rb | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/gc/mmtk/extconf.rb b/gc/mmtk/extconf.rb
index 5f4228972b..c0e788037e 100644
--- a/gc/mmtk/extconf.rb
+++ b/gc/mmtk/extconf.rb
@@ -15,6 +15,10 @@ create_gc_makefile("mmtk") do |makefile|
     MMTK_BUILD = debug
     LIBMMTK_RUBY = libmmtk_ruby.#$LIBEXT
     RUSTSRCS = #{rustsrcs.join(" \\\n\t   ")}
+
+    ifeq ($(MMTK_BUILD), debug)
+    CPPFLAGS += -DMMTK_DEBUG
+    endif
     MAKEFILE
   ]
 end